Treatment of hydrocarbon oils



Patented Apr. 17, 1934 UNITED STATES PATENT OFFICE TREATMENT OF HYDROCARBON OILS No Drawing. Application June 1, 1931, Serial No. 541,541

3 Claims.

This invention relates to the treatment of hydrocarbon oils and refers more particularly to the treatment of such oils to reduce their total sulphur content. More specifically the invention 5 comprises treating sulphur containing hydrocarbon oils with nitrides of metals to eifect reactions for the formation of sulphides of such metals with a resultant equivalent sulphur reduction in the oils under treatment.

The problem of partially or wholly desulphurizing hydrocarbon oils has been of major importance in the petroleum and allied industries for a long time. Various reagents of very diverse composition and characteristics have been employed with varying success, particular types of treatment being employed upon particular sulphur containing fractions obtained from crude petroleums by non-cracking or cracking distillation. The following is a list of some of the types of organic sulphur derivatives which have been identified in various petroleum fractions besides certain amounts of dissolved elementary sulphur and hydrogen sulphide: Mercaptans, sulphides or sulphur ethers, disulphides, thiophenes, thic- 26 phanes and the like.

Certain specific reagents are more reactive toward one group of derivatives than toward others and in many instances partial desulphurization may be effected by employing several reagents in 30 v stages. For example, it has been found practical to remove substantially all of dissolved hydrogen sulphide by the use of caustic soda or other alkalies; to remove mercaptans by the use of mercuric chloride which forms crystalline compounds and 85 the like. It is commonly found, however, that after the common and more readily obtainable treating reagents have been exhausted, that there,

is a content of residual sulphur remaining in the oils which has heretofore defied efiorts towards its removal, such residual sulphur having been found to becharacteristic oi sulphur constituting a part of the ring of cyclic compounds such as thiophene and its derivatives. It is with the removal of thistype as well as other types of such residual sulphur that the present invention is primarily concerned. i In one specific embodiment of the invention, it comprises treating hydrocarbon oils with nitrides of various metals.

Nltrides of metals may be manufactured by a variety of methods. The pure metal may be heated in an atmosphere of nitrogen to suitable temperatures necessary for the direct union of the nitrogen and the metal, the metal may be -heated with ammonia, the reaction in this case liberating nascent hydrogen, the amides or ir'nides of the metals may be heated with decomposition to produce metallic nitrides and free. hydrogen. By one or the other of these methods nitrides of the following metals have been prepared: Lith- 60 ium, strontium, barium, boron, aluminum, gerium, titanium, thorium, silicon, vanadium, tantalum, chromium, uranium, manganese; copper, mercury, iron, silver, cadmium, zinc, lead molybdenum, bismuth, antimony, and tungsten. The 66 properties of these nitrides vary widely ranging from compounds so unstable as to be explosive at the application of slight shock to those which are relatively stable at very'high temperatures. When mixtures of metals are employed in nitride 70 manufacture, the resulting products may be of the nature intermediate between those of the constituent bases and readily applicable to use according to the process of the invention. It is obvious from the preceding statements 7 as to the variations in physical and chemical characteristics of the nitrides of metals that their use as reagents for the treating of hydrocarbon oils will be dependent-upon the natureof the par-" ticular nitride or nitride mixture employed. Se lection is made with regard to the relative stability of the nitride under conditions of operation which have been found most suitable for the treating reactions. There will commonly be eliminated on the one hand such nitrides which are too unstable to be readily handled and on the other hand those compounds of metals and nitrogen which are too stable to react to the de sired extent with the oils.

Of the list of possible nitrides mentioned in the preceding paragraph a-lirnited number have been found to be of use in the process of the pres-. ent invention, the general properties of these being given in the following descriptive paragraphs.

Copper nitride (CllsN) This particular nitride is a greenish-black powder which begins to decompose at a temperature of about 570 F. It is reacted upon slowly by acids and caustic soda at ordinary temperatures and lends itself to use in the present invention particularly when the vapors being treated are mixed with steam.

Calcium nitride (CaaNz), strontium nitride (SI'sNz), barium nitride (BazNi). 'Thesen'itrides of the metals of the alkaline earth group are quite similar in properties. They are brown or yellow bodies, stable under very high temperatures in the absence of moisture but decomposableslowly in the presence of water of steam which reacts to produce ammonia. If acid -vapors are present they react with greater rapidity.

Magnesium nitride (MgsNz). This nitride is a greenish-yellow mass which reacts more vigorously with water and dilute acids than the other three nitrides of the alkaline earth metals and tends to decompose at lower temperatures. It may profitably be employed for desulphurizing purposes according to the process of the, invention in controllable admixture with the other three nitrides.

Aluminum nitride (AlN). This nitride is also quite stable under heat in the absence of mois ture but readily yields ammonia and aluminum oxide in reaction with water or steam or the corresponding aluminum sulphide with hydrogen sulphide and certain organic sulphur compounds.

Thorium nitride (ThaNr). This nitride is decomposed slowly by water but more rapidly by steam, and is generally more reactive than the nitrides oi the alkaline earth group already mentioned.

Manganese nitrides (MnsNz, MnaNz). These nitrides, which are formed from manganese amalgams when heated to a red heat in a current of nitrogen are slate-gray powders which evolve ammonia when heated in hydrogen or in contact with molten alkalies. They are attacked by steam at a rate depending upon temperature and pressure to form manganese oxides.

Iron nitrides (FesNz. FeiNz). The nitrides of iron are particularly adaptable to use in the present process. They may be formed by heating iron in a current of ammonia at temperatures in the neighborhood of 875 F. The dull gray powder resulting from this treatment contains some unchanged iron as well as iron nitrides, but owing to the magnetic properties of iron the unchanged portions may be removed by magnetic separators and the nitrides recovered more or less pure. These nitrides decompose at temperatures in the neighborhood of 400 F., in the presence of water or sulphur compounds to form on the one hand ferric oxide and on the other hand ammonium sulphides and ferrous sulphide.

Nickel nitride (NlzNz). This substance is a dull black powder which evolves ammonia when moderately heated with steam or when heated to redness in hydrogen.

'Cobalt nitride (COJNz). This compound is quite similar to the corresponding nickel compound and may be used under the same conditions.

In carrying out the process of desulphurization characteristic of the invention various types of equipment and modes of operation may be employed. In some instances the nitride may be added to the oil and maintained in suspension by mechanical stirring devices during heating of the oil under atmospheric or superatmospheric pressure, in other cases the nitride may be injected into the suction side of a circulating pump which passes the oil through a heating element whereintemperatures necessary for reaction are produced, the products of reaction being removed by settling in subsequent enlarged chambers or the vapors of the oils may be passed over stationary contact masses contained in vertical treating towers, etc. In some cases the nitride may be formed from ammonia or nitrogen introduced along with the oil or oil vapors and in short many methods of application may be employed. In the case of certain oils, amines or pyridines may result from the interaction of the nitride with thiophene sulphur. In other cases a certain amount of nitrogen in combination with metal may be evolved as the free element thus being utilizable in the regeneration of the nitrides used for the desulphurizing treatment.

As an example of the results obtainable by the.

application of the process of the invention a cracked distillate of approximately gasoline boiling point range produced by the cracking of a residual or topped crude characteristic of the West Texas producing area may be treated. This gasoline without chemical treatment may contain 0.5% total sulphur of which only 0.3% or 60% of the total may be removable by the use of caustic soda and sulphuric acid to amounts as high as 10 pounds of acid per barrel of oil treated. When the oil after treatment with caustic soda and sulphuric acid is further treated under pressure at a temperature of approximately 400 F., with approximately 5% dry magnesium nitride by weight, the sulphur content may be reduced as low as 0.05% with concurrent improvement in the color, color stability and gum content.

As another example, the vapors of approximate gasoline boiling point range from the secondary tower of a cracking process operating upon Mid- Continent residuum may be passed upwardly through a tower containing iron nitrides mixed with fullers earth in the approximate proportion of 50% by weight, a small amount of steam equivalent to approximately 1 pound per barrel of condensed distillate being added to the vapors. Such a distillate without this special treatment may be found to contain 0.25% sulphur which is only reducible to 0.15% by moderately sulphuric acid treatment. through the bed of iron nitrides in the manner described, the sulphur content of the condensed distillate may be 0.1% or lower and may require a considerably smaller'amount of sulphuric acid for its final treatment and stabilizing. For ex-- ample, the amount of acid needed may be reduced from 7 pounds "per barrel when the process is not used to 3 pounds per barrel when it is used.

I claim as my invention:

1. A process of desulphurizing the overhead product resulting from the cracking of hydrocarbon oil, which comprises subjecting said product in heated vaporous condition to the action of copp tride.

2. ln it desulphurization of hydrocarbon oils, the step comprising treating the oil with a nitride of a metal selected from the group which consists of copper, calcium, strontium, barium, magnesiurn, aluminum, thorium, manganese, iron. nickel, and cobalt under conditions permitting the reacting of the nitride with the sulphur content of the oil.

3. In the desulphurization of hydrocarbon oils, the step which comprises treating the oil with copper nitride under conditions permitting the reacting of the nitride with-the sulphur content of the oil.

RAYMOND E. SCHAAD.

When the vapors are passed. 

